Wow, neat MOC. The details on the (what I'm assuming is like a space bike/speeder) look great.

For embedding images, you have to right click on your flickr picture and choose an appropriate size that fits with Classic-Castle's guidelines (so do Medium 500 in this situation). Then, right click it again and choose 'copy image url'. Then come back to your Classic Castle post and choose the IMG button and paste what you copied by using CTRL+V on your keyboard and it will look like this:

or most Flickr users supply the option to already have the HTML/BBCode code prepared (Hint: C-C has BBCode). I couldn't find it on your specific MOC, but it's under the share tab on a Flickr photo. You would need to find the correct image size again, click on BBCode, and then highlight over all the text and use CTRL+C on your keyboard to copy. Then, you use CTRL+V to paste it into C-C posts. It would simply come out like this:

[url=http://www.flickr.com/photos/kcrmccoy/7481567062/][img]http://farm9.staticflickr.com/8153/7481567062_203ab67430_n.jpg[/img][/url][url=http://www.flickr.com/photos/kcrmccoy/7481567062/]John Hancock - High Five 2012 (1)[/url] by [url=http://www.flickr.com/people/kcrmccoy/]Casey M.[/url], on Flickr

Looking forward to more creations from you. You've got an eye for vignette-like MOCs.